Many different types of briquette forming or squeezing machines are known which employ a piston reciprocable in a perforated chamber, but most of these machines for large volumes and high pressures have a cylindrical configuration.
In view of scarcity of oil and the need to conserve it, and in view of the pollution problems in disposing of sludge containing substantial amounts of oil, such as sludges recovered from separators for coolants for cutting tools, it has become important that as much as possible of this type of oil be recovered from such sludges.
It has been found that to squeeze such sludges in previously known briquette forming machines, that the opening for the introduction of the sludge must have at least six inches minimum dimension, because of its tendency to bridge and block any narrower openings or ducts. Furthermore in order to economically squeeze large volumes of these sludges, a relatively large chamber is required. Then it was found, that if any particle in this chamber was more than about three inches, and preferably more than two inches from the filter screen in the chamber, only a minor amount of liquid or oil around such particle would penetrate the remaining compressed mass of particles to the screen and be removed. Thus, conventional briquetting chambers having a capacity for relatively large volumes of solids and producing pressures above about 250 psi, and preferably about 500 psi, were not sufficiently efficient to remove enough oil from such sludges to be practical.